1. Field of the Invention
This invention relates generally to the field of Surgery, and more particularly to instruments and cutters for performing intraocular surgery.
2. Description of the Prior Art
Beginning in the late 1950s and early 1960s, a number of modern methods for performing vitreous surgery were developed. These new methods included the development of a number of automated instruments to remove and replace vitreous.
Several of the instruments developed for these tasks have been illustrated and described by Hennig, J. & Bormann, H. in: Gerate zur Vitrektomie. Klin Monatsbl Augenheilkd 166:29, 1975; and by Peyman, G. A. & Sanders, D. R. in: Advances in Uveal Surgery, Vitreous Surgery, and the Treatment of Endophthalmitis. Appleton-Century-Crofts, 1975. All of these devices included a small tube or probe formed with an aperture near the tip and adapted to be inserted into the eye, an internal cutting tube or rotating burr, and some form of suction means for withdrawing severed tissue. The instruments employing rotating curring bits frequently wound up the fibrous tissue to be removed and tore the tissue rather than severed it. Nearly all of the present suction cutters operate in such a way that tissue must be drawn into an opening before it is severed by the cutting mechanism. Especially taut membranes resist this movement, however, and are difficult to manage.
In my earlier U.S. Pat. No. 3,776,238, entitled: OPHTHALMIC INSTRUMENT, there was described an instrument consisting of two tubes mounted coaxially within one another, and with an opening adjacent to the end of the outer tube. Cutting of the vitreous and fibrous bands was performed by a chopping action set up by the sharp end of the inner tube against the inner surface of the end of the outer tube.
The instrument described in this patent was found to have some limitations in use. For one, the chopping action tended to dull the cutting edge on the inner tube so that it would not cut cleanly thereafter. The failure to cut cleanly inhibited the removal by suction of the tissue severed.
The U.S. Pats. to O'Malley, Nos. 3,884,237 & 3,884,238, also describe APPARATUS FOR INTRAOCULAR SURGERY having a probe consisting of concentric tubes of small diameter. The inner tube is moved longitudinally within the outer tube to provide a cutting action at the edges of an aperture formed through the wall of the outer tube. Vitreous material to be severed is sucked into the aperture and sheared off by the cutting edge of the end of the inner tube. The aperture per se is generally triangular in configuration with the tapered sides and a base transverse to the axis of the tube. The orientation of the base is such that the cutting edge of the inner tube forces the vitreous material away, rather than shearing against the edge of the base.